alabaster

Alabaster sphinx at Memphis, carved from a single
block of alabaster.

Alabaster is a massive, fine-grained form of gypsum (calcium sulfate), usually translucent and white. It has been used ornamentally
for many centuries, being easily carved. In the Middle Ages alabaster was
cut into thin laminae for use in church windows, notably in Italy, e.g.,
San Vitale, Ravenna. It can also be dyed or made opaque by heating. Ancient
oriental alabaster was a yellowish marble.